1. Field of the Invention
The invention relates to a seal for valves, in particular for upper valve parts, consisting of a profiled ring of a rubber elastic material, in which a supporting ring is arranged.
2. Brief Description of the Prior Art
A seal of the above-mentioned type is known from the volume control valve described in DE-A1-3 206 481. The supporting ring in the known seal has a rectangular cross section; the profiled ring is formed as a lip seal. An annular recess with a rectangular cross section is provided in the profiled ring and accommodates the supporting ring. The external surfaces of the supporting ring and the profiled ring lie on the same cylindrical surface.
DE-C2-3 207 895 and DE-A1-2 944 520 disclose upper valve parts which in each case comprise a fixed valve seat disc (fixed disc) which is made of a ceramic material, is connected to the internal end face and on which a mobile valve seat disc (control disc) which is also of a ceramic material slides internally and against which a sealing ring rests externally. The sealing ring, which is prestressed, rests loosely against the fixed disc and the housing of the upper valve part and projects beyond the end face.
The sealing ring serves on the one hand as a seal for the housing and the fixed disc and on the other hand as a seal for a valve seat which is provided in a lower valve part with which the upper valve part co-operates. The use of the sealing ring means that the pressure of the component part assembly in the upper valve part cannot be accurately adjusted. Too great a pressure may make the parts stiff, while too low a pressure may result in leakages. Furthermore, due to the adhesive effect between the sealing ring and the valve seat, the upper valve part may unintentionally be dismantled. Unauthorised persons may dismantle the sealing ring.